Under certain circumstances, carbon dioxide,CO2(g), can be made to react with hydrogen gas,H2(g), to produce methane, CH4(g), and water vapor,H2O(g):
CO2(g)+4H2(g)→CH4(g)+2H2O(g)
How many moles of hydrogen gas would be needed to react with excess carbon dioxide to produce 76.6 moles of water vapor?